1. Technical Field
The present invention relates to a lighter which consumes hydrocarbon fuel such as butane and includes a spark producing means Specifically, the present invention relates to an improved spark producing means for a lighter which is more uniformly operatable.
2. Discussion of the Related Art
A conventional cigarette lighter includes a body containing a fuel reservoir filled with a liquified and pressurized hydrocarbon fuel, a valve actuator lever, a spark wheel, a flint in frictional contact with the spark wheel, and a fuel flow control valve in fluid communication with the fuel reservoir. After the spark wheel is rotated against the flint by digital manipulation to produce sparks, the valve actuator lever is depressed allowing gaseous hydrocarbon fuel to flow out of the reservoir through the flow control valve. The sparks then ignite the released fuel to produce a flame. Such lighters are known in the art and are commercially available.
Specific means for producing ignition sparks when contacting a pyrophoric flint in these lighters are also known in the art. For example, U.S. Pat. No. 4,509,916 to Le Boudec discloses a device for producing an ignition spark when contacting a flint. The device includes a flint cutting member made from helically-coiled wire with a circular cross section which includes saw-teeth projections for contacting and cutting the flint to create sparks. The flint, like the coiled wire, also includes a circular cross section. The device may be configured and adapted for use as a spark wheel in known lighters.
However, these related art spark producing means are disadvantageous in that irregular friction is produced between the flint and the user-rotatable spark wheel. This irregular friction leads to non-uniform rotational force requirements for rotating the spark wheel, and thus may increase the difficulty in producing ignition sparks.
More particularly, when a flint with a circular cross section is utilized in conjunction with a art spark wheel coil fashioned from wire with a circular cross section, the surface of the flint contacting the coil becomes deeply grooved over time so as to match the curved coil surface. The same difficulty can also arise with spark wheel assemblies having a flint cutting member made from a solid cylinder rather than coiled wire. Such solid cylinders are typically cut with a spiral groove on the outer surface to improve the spark creating characteristics of the part. This spiral groove in the cutting member can also result in a deeply grooved flint, such as encountered with the coiled wire cutting members. In addition, the rotation of such cutting members against the flint during use urges the flint to rotate about its central axis.
These two factors, i.e., the deep grooving of the flint surface (and resulting high ridges) and the urged rotation of the flint during use, are disadvantageous in combination as they bring about non-uniform user actuation of the spark wheel. More specifically, the flint, with a highly ridged/deeply grooved striking surface as shown in FIG. 7A, provides a significant non-uniform resistance to rotation of the spark wheel assembly as the cutting member is required to periodically breakdown the high ridges as it is rotated. The nonuniformity of the force required to rotate the spark wheel assembly can be increased further when the flint itself rotates on its axis as a result of the screw thread like action of the cutting member on the flint. Such rotation of the flint is difficult for the user to overcome due to the high ridges on the flint surface which require a relatively high force to break through.
Highly non-uniform resistance is especially disadvantageous in many of the newer child resistant lighters. For example, U.S. Pat. No. 5,483,978 to Doiron discloses a child resistant lighter with a guard which partially covers the spark wheel, thereby increasing the difficulty of rotating the same. This spark wheel cover, when combined with the non-uniform force requirements of the prior art spark producing means can result in non-uniform and unpredictable increases in the difficulty of lighter actuation by intended users.